Lithium halide batteries have become well known for their extended shelf life and suitability as the power source in cardiac pacer devices. Normally these batteries utilize a lithium anode and an organic charge transfer complex with an excess halide as the cathode material. U.S. Pat. Nos. 3,660,163, 3,674,562, and 4,148,975 are illustrative of such cells.
Because of the long life associated with such batteries, it is desirable to have a method for indicating the amount of life remaining. This is particularly important in cardiac pacer devices so as to afford adequate time for the surgical removal of the power source before it dies. It is, therefore, an object of the present invention to provide a means within the battery for positively indicating the remaining life of such batteries without requiring any modification to the electronic circuitry of the pacer device. It is a further object to the present invention to provide a battery whereby it is possible to determine the remaining energy available, which can be interpreted into remaining time, regardless of the previous service to which the cell had been subjected.